A proton-exchange membrane fuel battery is a battery generating electric power by using a principle of gaining electricity in the process of reacting hydrogen with oxygen (an air) so as to obtain water. The fuel battery is constituted by a fuel battery stack in which a cell is formed by an electrolyte membrane transmitting hydrogen ions and two separators between which the electrolyte membrane is inserted and a plurality of the cells are layered. In this case, a function of shielding the hydrogen and the oxygen, and conductivity capable of gaining the electricity are required in the separator forming the cell.
Further, since the hydrogen, the oxygen and cooling water are used within the stack, a gasket for sealing them is assembled together. However, since a considerable man-hour is required for assembling the gasket within the stack after the gasket having been independently formed, a method of integrally forming the gasket in a separator main body has been proposed, and there has been also proposed a method of forming a gasket forming groove on a surface of a separator main body for preventing a gasket lip from being displaced due to an internal pressure and forming a through hole within the gasket forming groove, thereby fixing the gasket to both the surfaces of the separator main body on the basis of an anchor effect of the through hole, for example, in the invention described in Japanese Unexamined Patent Publication No. 2001-185174.
On the other hand, a material of the gasket conventionally employed is silicone rubber corresponding to liquid rubber having low viscosity, however, there have been generated problems such as transmission of hydrogen, precipitation of silicone, swelling of silicone rubber and the like. As a countermeasure thereof, it has been proposed, by the invention described in Japanese Unexamined Patent Publication No. 2002-50369, that EPDM or fluorine-contained rubber corresponding a compound type rubber having high viscosity is used in place of the silicone rubber.
However, in the case that the gasket is integrally formed in the separator main body, the silicone rubber can be formed at low injection pressure and gives no damage to the separator due to the low viscosity in the liquid phase of the silicone rubber. However, in the case of using the EPDM or the fluorine-contained rubber is used, high injection pressure is required due to the high viscosity, so that as shown in FIG. 10, there are generated a problem that a bottom surface 10a or 11a of the gasket forming groove is punched out by the rubber pressure, and a problem that a groove bottom surface corner portion 14 is punched out by the rubber pressure in a portion in which a side surface strength of the gasket forming groove is low, whereby a damage portion 15 is generated. Accordingly, there has been a problem that a sealing performance is deteriorated due to the damage of the separator main body.
Further, when the separator main body is made thinner for making the fuel battery compact in size and light in weight, there has been a problem that a bottom surface of the forming groove and a corner portion of the groove bottom surface are damaged at a time of forming with the liquid rubber or the like under low injecting pressure. Further, even in the gasket forming groove having the structure in which the through hole is not provided, when a groove such as a forming groove, an adhesion groove or the like is formed in the back of the gasket forming groove, a stress is concentrated, so that there is a problem that the bottom surface of the gasket forming groove is damaged.
Patent Document 1: Japanese Unexamined Patent Publication No. 2001-185174
Patent Document 2: Japanese Unexamined Patent Publication No. 2002-050369